This invention relates to a system and method of controlling the output of a fiberoptic phototherapy pad, and, more particularly, to a system and method for sensing the light intensity of a fiberoptic phototherapy pad and for providing a servocontrol to deliver a prescribed amount of light therapy to an infant.
Hyperbilirubinemia is an affliction of newborn infants typified by an elevated level of a toxic molecule known as bilirubin in the infant's blood. Current medical therapy for such affliction is through the use of phototherapy where light radiation, generally within certain desired wavelengths, is directed upon the infant's skin. The most widely used means currently is through banks of lights that are placed over the infant and which direct the light in the desired path to impinge upon the infant. While effective, such lights are cumbersome in that they interfere with personnel attending to the infant and also generate undesirable heat surrounding those personnel. Additionally, since such lights are occasionally moved, adjusted, turned off for various reasons during attending the infant, it is difficult to accurately access the actual amount of phototherapy provided to the infant.
A more recent innovative commercial means of combatting hyperbilirubinemia is by means of a fiberoptic light pad or blanket that is made of optic fibers. One such commercial product is shown and described in Daniel, U.S. Pat. No. 4,234,907 and where the optical fibers are used as warp fibers in a commercial loom and woven with normal threads (weft threads) to produce a fabric having interwoven optical fibers and regular threads. As the optical warp fibers are woven with the weft fibers, the bending of the optic fibers emits the light in a desired pattern.
There are many advantages to the fiberoptic pad over the conventional light systems, one of them being that the pad itself contacts the infants skin and therefore the light actually reaching the infant is more accurately controlled since each infant may have the fiberoptic pad placed in the same relative position with respect to its skin. Thus, unlike lights that may be varied, moved etc, the dosage afforded to the infant can be accurately administered.
With the advent of accurate administration, therefore, it is now possible and desirable to precisely apply a known amount of light therapy to the infant. Additionally, as the science of light therapy advances, more insight is being gained with respect to the amount of light and the desirable wavelengths to be utilized. As to the wavelengths, an improvement to the accuracy of the wavelength of light incident on the infant is provided by the use of a monochromatic light source such as a laser as disclosed in copending U.S. Patent application entitled "Laser Phototherapy" and assigned to the present assignee.
Likewise, since precise wavelengths are thus possible and clinicians can thus study the effect of differing wavelengths on the reduction of bilirubin, it still remains that the dosage or light density cannot be accurately controlled. At present there is no means of accurately determining the dosage of light therapy and therefore no means of applying a known dosage to the infant.
As a part of the problem of controlling the dosage, even if a known intensity of light is established at a phototherapy pad, over time, the light source may diminish and therefore the light originally established becomes more and more reduced with time. With no means of detecting that reduction and taking some compensating steps, the attempt at delivering an accurate dosage, predetermined dosage is difficult.
That the dosage is important in reducing bilirubin; note the Abstract of a paper presented at The American Pediatric Society, Society of Pediatric Research at New Orleans, La. in May of 1991 entitled, "Bright Light is The Right Light: Multicenter Trial of a Novel Phototherapy Device" in which the efficacy of phototherapy was improved by increasing the intensity of the light radiation applied to the infant.